This application proposes to develop a noninvasive pulmonary function test for use in infants and young children based upon the forced pressure oscillation method. Such a technique has been tested successfully in adults but has not been extensively evaluated in infants and newborns.The method is based upon the application of pressure oscillations over a range of frequencies to the airway opening or the thorax. Changes in the mechanical properties of the respiratory system alter the flow response of the respiratory system despite lack of patient cooperation or significant patient contact, and can be identified by advanced engineering techniques. A major advance is that the technique can separate airway from tissue properties. The long term goal of the application is the development of a commercially viable product.